Various structural components are used to form a typical aircraft. For example, wing and empennage surfaces of an aircraft typically include stringers that are coupled to skin members on the wing and empennage surfaces that cooperatively provide a desired flexural and torsional stiffness to the wing and empennage surfaces.
Aircraft structures may be formed from composite materials, which are generally reinforced polymer-based materials used in place of metals, particularly in applications in which relatively low weight and high mechanical strength is desired. Accordingly, composite materials are widely used in a variety of commercial and military aircraft, terrestrial vehicles and consumer products.
A composite material typically includes a network of reinforcing fibers that are generally applied in layers, and a polymeric resin that substantially wets the reinforcing fibers to form a binding contact between the resin and the reinforcing fibers. The composite material may then be formed into a structural component by a variety of known forming methods, such as an extrusion process or other forming processes.
In an aircraft, a stringer may be used to transfer bending loads in skin panels, and stiffen the skin panels in order to prevent buckling, for example. The stringers and skin panels may be made of composite materials, such as carbon fiber reinforced plastic (CFRP). A composite stringer may be fabricated from multiple plies of reinforcing fibers.
After a composite structure is initially formed, the composite structure may be cured, such as within an autoclave. Various structures that are used to form an aircraft have arcuate and/or irregular shapes. The composite structures are typically positioned on or within molds during a curing process. Often, the molds are also formed of composite materials. As such, the molds themselves are cured. However, because the molds may have irregular and/or arcuate shapes, the molds may be unevenly cured. For example, a flat surface of the mold may be evenly cured, but curved portions of the mold may be unevenly cured due to the curing device (such as a lamp) being spaced a different distance from the cured portion than the flat surface.